The Gracies are of Scottish descent, so maybe that has something to do with it. I am not sure about where he falls in the lineage or family tree. He has probably been living in the US for a while, but he still has an accent.
look at carlos's side of the family, they dont look anything like the helio side... Carlos, Carlinhos, Cesar, Reylson, Carley, Rocian, Rosiley, Carlson, Robson...... They are all scottish/american looking
and roger gracie is the one that his last name isnt gracie... his mom is a gracie but his dad isnt but he sports the family name